package time

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"

	"apigo.cc/go/cast"
)

// Parse 将任意类型转换为 time.Time。
// 支持：time.Time, 时间戳 (秒/毫秒/微秒/纳秒), RFC3339, JS 格式, 中文格式等。
// 转换失败返回当前时间 time.Now()。
func Parse(v any) time.Time {
	if v == nil {
		return time.Now()
	}

	if tm, ok := v.(time.Time); ok {
		return tm
	}

	str := strings.TrimSpace(cast.String(v))
	if str == "" {
		return time.Now()
	}

	var tm time.Time
	var err error

	// 1. 处理纯数字 (时间戳或紧凑格式)
	if num := cast.Int64(v); num > 0 {
		// 紧凑格式解析
		switch len(str) {
		case 14: // 20060102150405
			if tm, err = time.ParseInLocation("20060102150405", str, time.Local); err == nil {
				return tm
			}
		case 8: // 20060102
			if tm, err = time.ParseInLocation("20060102", str, time.Local); err == nil {
				return tm
			}
		case 6: // 150405 或 060102
			if tm, err = time.ParseInLocation("150405", str, time.Local); err == nil {
				return tm
			}
			if tm, err = time.ParseInLocation("060102", str, time.Local); err == nil {
				return tm
			}
		}

		// 时间戳处理
		switch {
		case num < 1e10: // 秒
			return time.Unix(num, 0)
		case num < 1e13: // 毫秒
			return time.UnixMilli(num)
		case num < 1e16: // 微秒
			return time.UnixMicro(num)
		default: // 纳秒
			return time.Unix(0, num)
		}
	}

	// 2. 标准格式与常见变体
	// RFC3339 (带 T 和 Z 或偏移量)
	if strings.Contains(str, "T") {
		if tm, err = time.Parse(time.RFC3339Nano, str); err == nil {
			return tm.In(time.Local)
		}
		if tm, err = time.Parse(time.RFC3339, str); err == nil {
			return tm.In(time.Local)
		}
		// 兼容带 T 但没 Z 的情况，尝试按普通日期时间解析
	}

	// 处理分隔符：-, /, .
	if len(str) >= 10 && (str[4] == '-' || str[4] == '/' || str[4] == '.') {
		sep := str[4]
		layout := fmt.Sprintf("2006%c01%c02", sep, sep)
		
		// 完整日期时间
		if len(str) >= 19 {
			tsep := str[10] // 通常是 ' ' 或 'T'
			if len(str) >= 20 && str[19] == '.' {
				// 带纳秒
				if tm, err = time.ParseInLocation(layout+fmt.Sprintf("%c15:04:05.999999999", tsep), str, time.Local); err == nil {
					return tm
				}
			} else {
				if tm, err = time.ParseInLocation(layout+fmt.Sprintf("%c15:04:05", tsep), str[:19], time.Local); err == nil {
					return tm
				}
			}
		}
		// 纯日期
		if tm, err = time.ParseInLocation(layout, str[:10], time.Local); err == nil {
			return tm
		}
	}

	// 06-01-02 这种短年份格式
	if len(str) >= 8 && (str[2] == '-' || str[2] == '/' || str[2] == '.') {
		sep := str[2]
		layout := fmt.Sprintf("06%c01%c02", sep, sep)
		if len(str) >= 17 && (str[8] == ' ' || str[8] == 'T') {
			if tm, err = time.ParseInLocation(layout+fmt.Sprintf("%c15:04:05", str[8]), str[:17], time.Local); err == nil {
				return tm
			}
		}
		if tm, err = time.ParseInLocation(layout, str[:8], time.Local); err == nil {
			return tm
		}
	}

	// 3. 特殊格式：JS, HTTP, 中文
	if strings.Contains(str, "GMT") || strings.Contains(str, "CST") {
		// 简单清理 JS 冗余部分
		cleanStr := strings.SplitN(str, " (", 2)[0]
		// 统一将时区简写替换为偏移量尝试解析
		cleanStr = strings.Replace(cleanStr, "CST", "+0800", 1)
		
		formats := []string{
			"Mon Jan 02 2006 15:04:05 GMT-0700",
			"Mon, 02 Jan 2006 15:04:05 GMT",
			time.RFC1123Z,
			time.RFC1123,
			time.UnixDate,
		}
		for _, f := range formats {
			if tm, err = time.Parse(f, cleanStr); err == nil {
				return tm.In(time.Local)
			}
		}
	}

	// 中文格式解析
	if strings.ContainsAny(str, "年月日时点分秒") {
		return parseCN(str)
	}

	// 纯时间格式
	if strings.Contains(str, ":") {
		if tm, err = time.ParseInLocation("15:04:05.999999", str, time.Local); err == nil {
			return tm
		}
		if tm, err = time.ParseInLocation("15:04:05", str, time.Local); err == nil {
			return tm
		}
		if tm, err = time.ParseInLocation("15:04", str, time.Local); err == nil {
			return tm
		}
	}

	return time.Now()
}

// Format 格式化时间。
// layout 支持: YYYY-MM-DD HH:mm:ss, YYYY/MM/DD, HH:mm 等直观格式。
func Format(layout string, v any) string {
	tm := Parse(v)
	l := layout
	l = strings.ReplaceAll(l, "YYYY", "2006")
	l = strings.ReplaceAll(l, "YY", "06")
	l = strings.ReplaceAll(l, "MM", "01")
	l = strings.ReplaceAll(l, "M", "1")
	l = strings.ReplaceAll(l, "DD", "02")
	l = strings.ReplaceAll(l, "D", "2")
	l = strings.ReplaceAll(l, "HH", "15")
	l = strings.ReplaceAll(l, "hh", "03")
	l = strings.ReplaceAll(l, "h", "3")
	l = strings.ReplaceAll(l, "mm", "04")
	l = strings.ReplaceAll(l, "ss", "05")
	l = strings.ReplaceAll(l, "a", "pm")
	l = strings.ReplaceAll(l, "A", "PM")
	l = strings.ReplaceAll(l, "ZZ", "-0700")
	l = strings.ReplaceAll(l, "Z", "-07:00")
	return tm.Format(l)
}

// Add 时间加减 DSL。
// 格式如: "+1Y-2M+3D", "+1h30m", "-1s"。
// 单位支持: Y (年), M (月), D (天), h, m, s, ms, us, ns。
func Add(expr string, v any) time.Time {
	tm := Parse(v)
	if expr == "" {
		return tm
	}

	i := 0
	years, months, days := 0, 0, 0
	var duration time.Duration

	for i < len(expr) {
		sign := 1
		if expr[i] == '+' {
			i++
		} else if expr[i] == '-' {
			sign = -1
			i++
		}

		j := i
		for j < len(expr) && expr[j] >= '0' && expr[j] <= '9' {
			j++
		}
		num := 1
		if j > i {
			num, _ = strconv.Atoi(expr[i:j])
		}
		val := num * sign

		i = j
		unit := ""
		// 匹配双字符单位 (ms, us, ns)
		if i+2 <= len(expr) {
			u2 := expr[i : i+2]
			if u2 == "ms" || u2 == "us" || u2 == "ns" {
				unit = u2
				i += 2
			}
		}
		// 匹配单字符单位
		if unit == "" && i < len(expr) {
			unit = expr[i : i+1]
			i++
		}

		switch unit {
		case "Y": years += val
		case "M": months += val
		case "D": days += val
		case "h": duration += time.Duration(val) * time.Hour
		case "m": duration += time.Duration(val) * time.Minute
		case "s": duration += time.Duration(val) * time.Second
		case "ms": duration += time.Duration(val) * time.Millisecond
		case "us": duration += time.Duration(val) * time.Microsecond
		case "ns": duration += time.Duration(val) * time.Nanosecond
		default:
			// 默认秒
			duration += time.Duration(val) * time.Second
		}
	}

	if years != 0 || months != 0 || days != 0 {
		tm = tm.AddDate(years, months, days)
	}
	return tm.Add(duration)
}

// 辅助函数

var cnDateRegex = regexp.MustCompile(`(\d{2,4})?年?(\d{1,2})月(\d{1,2})日`)
var cnTimeRegex = regexp.MustCompile(`(上午|下午)?(\d{1,2})(?:时|点|：)(\d{1,2})(?:分|：)(\d{1,2})?秒?`)

func parseCN(str string) time.Time {
	str = strings.ReplaceAll(str, "：", ":")
	str = strings.ReplaceAll(str, " ", "")
	var y, m, d, h, mm, s int
	if matches := cnDateRegex.FindStringSubmatch(str); len(matches) == 4 {
		y = cast.Int(matches[1])
		m = cast.Int(matches[2])
		d = cast.Int(matches[3])
		if y > 0 && y < 100 { y += 2000 }
	}
	if matches := cnTimeRegex.FindStringSubmatch(str); len(matches) == 5 {
		h = cast.Int(matches[2])
		mm = cast.Int(matches[3])
		s = cast.Int(matches[4])
		if matches[1] == "下午" && h < 12 { h += 12 }
		if matches[1] == "上午" && h >= 12 { h -= 12 }
	}
	if y == 0 { y = time.Now().Year() }
	if m == 0 { m = int(time.Now().Month()) }
	if d == 0 { d = time.Now().Day() }
	return time.Date(y, time.Month(m), d, h, mm, s, 0, time.Local)
}

// Helpers

func Now() time.Time { return time.Now() }
func Today() time.Time { return time.Date(time.Now().Year(), time.Now().Month(), time.Now().Day(), 0, 0, 0, 0, time.Local) }
func Yesterday() time.Time { return Today().AddDate(0, 0, -1) }
func Tomorrow() time.Time { return Today().AddDate(0, 0, 1) }